Correct Understanding of Big Bang Theory

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Discussion Overview

The discussion revolves around the understanding of the Big Bang Theory, specifically the nature of the singularity at the moment of the Big Bang and its implications in relation to general relativity and quantum mechanics. The scope includes theoretical interpretations and conceptual clarifications regarding singularities and their properties.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the correctness of the idea that everything in the universe was condensed into a singularity at the moment of the Big Bang.
  • Another participant asserts that, according to general relativity, the universe was indeed condensed into a singularity of infinite density at the moment of the Big Bang, but notes that quantum effects complicate this understanding.
  • A third participant relates the discussion to black holes, suggesting that while relativity predicts a singularity, quantum theory introduces uncertainties about the nature of such singularities.
  • Another participant challenges the notion of a singularity as a "single point," arguing that in certain models, the concept of a singularity may not be well-defined and raises questions about the implications of infinite density.

Areas of Agreement / Disagreement

Participants express differing views on the nature of singularities and the implications of general relativity versus quantum mechanics. There is no consensus on the definition or characteristics of a singularity, indicating ongoing debate and uncertainty.

Contextual Notes

The discussion highlights limitations in current theories regarding singularities, particularly the lack of a complete quantum gravity theory and the ambiguity in defining singularities in different models.

Lord Draco
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Is this correct?

Before the big bang or at the moment of the big bang(since we don't know what happened before the big bang), from my understanding it is believed that everything in the universe was all condensed into a singularity, a single point of all the energy of the universe. is this correct?
 
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This is correct according to pure GR, at the moment of the BB the universe was condensed into a singularity of infinite density. However at some point, as one approaches the BB under time reversal, GR is expected to yield to quantum effects; what these effects might do can only be predicted by a quantum gravity theory, unfortunately we do not have such a theory - yet.

Garth
 
Garth's description is also relevant to the question of what goes on inside a black hole. Relativity predicts a condensation to a point singularity, but quantum theory gets in the way and we really don't know what goes on.
 
Even in ordinary general relativity, it's not necessarily true that a singularity is a "single point". In a model where the universe is spatially infinite, you can say that the density goes to infinity at the singularity, and you can say that the distance between any two points which are some finite distance apart at a later time goes to zero at the singularity, but I don't think it necessarily makes sense to call the singularity a "point", its size wouldn't be well-defined (it's sort of like the question, 'what's zero times infinity'?)
 

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